T REPRO N DU LA C The International Journal of Plant Reproductive Biology 10(2) July, 2018, pp.184-188 P T I F V O E Y B DOI 10.14787/ijprb.2018 10.2. I T O E I L O C G O S I S E T S H Reproductive biology of dancing girl ginger, Globba schomburgkii (Zingiberaceaeae) T Aswani K. and M. Sabu* Angiosperm Taxonomy and Floristics Division Department of Botany, University of Calicut, Kerala – 673635, India *e-mail: [email protected] Received: 28.03.2018; Revised: 29.05.2018; Accepted: 01.01.2018; Published online: 01.06.2018 ABSTRACT Globba schomburgkii (Zingiberaceaeae) is an ornamental ginger with a very conspicuous floral display, but almost no fruit set under field condition. The pollination biology of G. schomburgkii was studied to determine the pollination system and the reason for fruitlessness. Studies were conducted over two consecutive years (2016 and 2017) at Calicut University Campus, Kerala, India. Phenological studies indicated that the species shows a regular flowering season. Flowers are zygomorphic and hermaphrodite. The flowers are mainly visited by Amegilla zonata, which is the effective pollinator. The study confirmed that low percentage of pollen viability is responsible for the fruitlessness and the plant is vegetatively propagated, bulbils being the main propagules. Keywords : Amegilla zonata, Bulbils, Globba schomburgkii, Pollination biology. Globba (Zingiberaceae–Zingiberales) consists of ca. 100 Botanical Garden (CUBG) in Kerala, India (11°25´N & species of small perennial herbs from East Asia and Malaysia 75°50´E) during 2016 and 2017. (Box and Ruddell 2005). Flowers of Globba are striking Flower morphology—Floral morphology was studied in the orange, yellow, purple or white, contrasting with the often field and also in the laboratory with the help of a green inflorescence bracts (Endress 1994, Takano and Okada stereomicroscope (Leica M80). The measurements of the 2003). They possess extraordinarily specialized morphology, floral parts were taken with the help of scale. By direct visual even within the context of Zingiberaceae, in which there is observation, the colour of the flower was determined. The invariably a single fertile stamen (the adaxial stamen) and two presence of smell of these flowers was detected by keeping sterile inner androecial members are fused and petaloid, some flowers in bottles for two hours. forming an abaxial labellum (Kirchoff 1997, 1988a, b, Flowering phenology—Flowering phenology was observed Endress1994, Box and Ruddell 2005). in the field in two flowering seasons in 2016 and 2017. G. schomburgkii is an ornamental ginger, commonly Frequent visits were made to the study sites to observe the known as dancing girl ginger. It is distributed mainly in flowering season. Regular observations were carried out from Eastern India, Myanmar, Thailand, Vietnam, and South China. the period of inflorescence initiation to the period of fruit Each stem produces a terminal inflorescence. Beautiful maturation. Anthesis and anther dehiscence was observed in golden yellow flowers are borne in a pendulous raceme or the field using hand lens, following the method of Reddi and thyrse (Sabu 2006). Janaki Bai (1981), Mathur and Mohan Ram (1986), Pollination biology is poorly known in Globba and other Ramasubbu et al. (2009). Zingiberaceae (Endress 1994, Ippolito and Armstrong 1993). Nectar volume and sugar concentration—To estimate the G. schomburgkii produces mass flowers and pollination take volume of nectar and sugar concentration flowers were place, but there is no fruit set. Pollination can be the first factor randomly selected from different plants and bagged just limiting fruit production (Schemske 1980, Howell and Roth before opening to prevent floral visits. They were excised at 1981, Arista et al. 1999), and the study of the reproductive hourly intervals (N=50) and the amount of nectar was ecology of flowering plants is important for determining determined using micro pipette (10 µl) and the concentration barriers to seed and fruit set (Gao et al. 2006). So we decided to of nectar by using calibrated hand refractometer (WZ 103 study the reproductive biology of G. schomburgkii. Here we BRIX 0 – 32, China). present the results of our investigations, which addressed the Pollen biology—In Zingiberaceae pollen morphology is following questions concerning the reproductive biology of G. determined by mounting pollen grains directly in glycerine schomburgkii: (i) what are the flower morphology, floral jelly after killing and fixing fresh pollen grains in 70% alcohol phenology, pollen biology of G. schomburgkii? (ii) What are and washing it in distilled water (Mangaly and Nayar 1990), the barriers to fruit set? (iii) What are the main visitors to G. because acetolysis dissolved the pollen completely in majority schomburgkii, and are they effective pollinators? of Zingiberaceous taxa. Photomicrographs of the sample were taken at appropriate magnification using Zeiss Axiolab A1 MATERIALS AND METHODS stereomicroscope. The average size of pollen grains was Study plant—The study was conducted on different measured from a random sample of 100 pollen grains in each populations of G. schomburgkii (Fig.1A) at Calicut University species by using Axiovision 4.8 software. The biochemical 2018 Reproductive biology of Globba schomburgkii (Zingiberaceaeae) 185 Fig.1-Globba schomburgkii. A. Habit. B. Inflorescence. C. Single flower. D. Floral development. E. Winged anther. F. Stigma. G. Pollen viability. H. Pollen germination. I. Eurema hecabe. J - L. Pollinator –Amegilla zonata. M. Udaspus folus. N. Bulbils. O. Seedlings. 186 The International Journal of Plant Reproductive Biology 10(2) July, 2018, pp.184-188 analysis of pollen grains was done using IKI, sudan black B short inflorescence (cincinnus) in a zig-zag arrangement. This and Coomassie brilliant blue R for the detection of starch, is similar in other Globba spp. reported earlier (Box and lipid, and protein, respectively. The viability of pollen grains Rudall 2006). The flowers are golden yellow in colour was assessed by Triphenyl tetrazolium chloride test (Shivanna (Fig.1C).The floral tube is long. The labellum is triangular and Rangaswamy 1992). Pollen-ovule ratio was calculated as with divergent lobes, golden yellow in colour with orange per the method suggested by Cruden (1977). The effect of patch at the centre. Flowers produce a single fertile stamen organic and inorganic nutrients on in vitro pollen germination (Fig.1E); labellum is the prominent landing platform for small and pollen tube elongation were studied using Brewbaker and insects. Anther is small with two spreading, narrowly Kwack’s medium, solutions of boric acid (100 - 500 μg/l), triangular appendages on each side on a long arching filament, calcium nitrate (25 - 500 μg/l), magnesium sulphate (25 - 500 like a bow. The characteristic anther wings are believed to μg/l), potassium nitrate (25 - 500 μg/l) and glucose solution (1 function as levers, which allow the anther to be oriented into a - 40 μg/l). The percentage of pollen germination and pollen favourable position for the transfer of pollen; their lateral tube elongation were observed under Lab. A1 ZEISS Axiolab position may orient the anther correctly if the flower is compound microscope (Zeiss, Germany). approached laterally by the pollinator (Endress 1994). The Stigma receptivity—To check the receptivity of the stigma, pistil was well demarcated into ovary, style and stigma. Ovary cytochemical localization of non-specific esterases was was inferior and unilocular with many ovules borne on parietal conducted by hydrolysis of the substrate α-napthyl acetate placenta. Style was slender and long. The stigma (Fig.1F) was (Mattson et al. 1974) and also using hydrogen peroxide (H2O2) colourless, funnel-shaped with ciliate margin composed of reaction after Scribailo and Usher (1984). stiff bristles and clasped between the enlarged thecae of Pollination biology—The number of floral visitors, visiting stamen. Floral characters are incorporated in Table 1. time, foraging nature, foraging hour, time spent in each flower Table 1– Floral characters of G. schomburgkii was recorded by using stop watch, stigma touch by insects and frequency of visit were recorded during 30 days per each S. No. Floral characters Observations flowering period. The visitors were trapped by a net and 1. Flowering period June to August transferred them into a bottle containing a piece of filter paper 2. Flower type Zygomorphic, Hermaphrodite dipped in ethyl acetate. Collected visitors were transferred to a 3. Flower colour Golden yellow with orange glass slide and observed under a microscope. Pollination patch at the center efficiency of different pollinators was studied by observing 4. Odour Present the pollen loads on different body parts according to the 5. Nectar amount 67.6±2.5µl procedure given by Kearns and Inouye (1993). To check 6. Nectar concentration 5.30 – 6.30 a.m. pollen load on stigmatic surface, stigmas (n = 50) were 7. Anthesis time 10.30 – 11.00 a.m. 8. Anther dehiscence time Longitudinal slit collected after each visit of insects and observed under a 9. Anther dehiscence mode 1 microscope.The insects were identified by an entomologist, at 10. Number of anthers / flower 2647±112 the Trust for Animal Taxonomy, Zoological Survey of India, 11. Mean number of pollen 25±3 Kozhikode. grains / flower Breeding system—The breeding system determination 12. Mean number of ovules / 106.1 methods were adapted from Wong and Sun (1999). Breeding flower behaviors (autogamy, geitonogamy and xenogamy) was tested 13. Pollen - ovule ratio Granulate using controlled pollination studies in emasculated and 14. Pollen type 54.82±3.43µm 15. Pollen size Round or spherical bagged flowers. Self- and cross-pollination experiments were 16. Pollen shape Wet type performed by dusting pollen obtained from freshly dehisced 17. Stigma type 13.27±2.35 anthers on the receptive stigma. The pollinated flowers were 18. Pollen viability (%) 28±4 re-bagged and observed periodically for fruit formation. 19. Number of bulbils 6.00 – 7.00 p.m.